1. Field of the Invention
The present invention relates to a semiconductor component, and more particularly to a semiconductor component having a semiconductor body exhibiting four layers of alternating conductivity type, in which an outside n-emitter layer has a cathode contact, an outer p-emitter layer has an anode contact, and two base layers are provided respectively adjacent and between the outer emitter layers, and in which the anode and cathode respectively have terminals for an external circuit, and in which a metal-insulator-semiconductor structure is disposed adjacent the n-emitter layer (p-emitter layer), the metal-insulator-semiconductor structure being provided with a gate electrode insulated from the boundry surface of the semiconductor body and representing a controllable emitter short-circuit.
2. Description of the Prior Art
A component is known from U.S. Pat. No. 3,243,669, fully incorporated herein by this reference, of such type that, given a voltage poled in the forward conducting direction applied between the anode and cathode, the component is either conditioned to a first switching state in which it is low-resistant and current-conducting or in a second switching state, which is also designated as the block state, in which practically no current flows between the anode and cathode. The metal-insulator-semiconductor (MIS) structure thereby comprises a p-conductive zone extending from a boundary surface and disposed adjacent the p-emitter layer, a part of the p-emitter layer at the edge side and of the gate electrode insulated from and covering the boundary surface between the two aforementioned portions, whereby the p-conductive zone is embedded in the n-base layer and is connected to the n-base layer by a conductive coating located on the boundary surface. Upon the application of a control voltage to the gate electrode, a short circuit path is switched operative, the short circuit path bridging the pn junction between the p-emitter layer connected to the anode and the adjacent n-base layer. This action results in switching from the current-conducting state into the blocked state. The transition from the blocked into the current-conductive state occurs by a bridging of the pn junction between the p-base layer and the n-base layer by a further MIS structure which is also provided with a gate electrode.
It is also known from the German allowed and published application No. 24 38 894 to provide a semiconductor component of the type mentioned above with fixed emitter short circuits which comprise projections of the p-base layer which are conductively connected to the cathode. These effect a good stabilization of the component, i.e. high security against unintentional trigger operations give occurrence of voltages at the anode/cathode segment which are poled in the forward conducting direction, the voltages sometimes arising very quickly (high dU/dt loads).
What is disadvantageous is that the emitter short circuits required because of good stabilization easily lead to thermal overloads of the component given intentional or unintentional trigger operations. In the transition from the blocked state into the current-conducting state, in particular, a very thin current path is first formed between the anode and cathode, the path then subsequently expanding until the entire cross-section of the semiconductor component becomes current-conducting. The propagation speed of the edge of the respectively current-conducting surface, as measured in the boundary surface containing the n-emitter layer or the p-emitter layer, amounts to only approximately 0.01-0.1 mm/.mu.s given components provided with emitter short circuits. This, however, leads to high turn-on losses, and, therefore, to a lower current load capacity.